Low-drop-out (LDO) regulators are widely used, and may have programmable output voltages. The output voltage selection for an LDO regulator may be implemented within its feedback network.
FIG. 1 is a circuit diagram of an LDO regulator. Reference number 1000 generally denotes the LDO regulator as a whole, which includes a differential amplifier 100 and a feedback network 200. The electrical couplings of the amplifier 100 are a DC power supply terminal 105, a power reference terminal 104 which may be grounded and is denoted GND, an output terminal 101 which forms the LDO regulator output, an inverting input terminal 102 which is coupled to the output terminal 101 via the feedback network 200, and a non-inverting input terminal 103 which is connected to a reference voltage supply 300. VDD is the DC power supply voltage, VREF is the voltage of the reference voltage supply 300, which may be obtained from the silicon bandgap value, and VFB is the voltage which is supplied by the feedback network 200 to the inverting input terminal 102. Due to the operation of the differential amplifier 100, VFB may equal VREF. Then, the output voltage VOUT at the output terminal 101 may be G*VREF, where G is the division factor of the feedback network 200, and is greater than unity.
New feedback network designs for use with LDO regulators are desirable.